Electrical measuring instrument.



WILLIAM I. BRADSHAW, F 'VILKINSBURG', PENNSYLVANIA, SSIGNOR T0 NESTING- HOUSE ELECTRIC AND JINUFACTURING COMPANY, A CORPORATION 0F PENNSYL- veure.

To all whom it may concern.'

Be it known that I, IVILLIAM M. BRAD- sHAW, a citizen of the United States, and a resident of lVilkinsburg, in the county of Allegheny and 'State of Pennsylvania, haye ing instruments and. particularly to motor,

meters:

@ne object of my invention is to provide means for adapting a motor meter to operate correctly on a wide range of applied voltage.

Another object of my invention is to provide the magnetic circuit of a motor meter with means for deilecting a relatively large part of its main magnetic linx through its armature at predetermined times.

' Heretofore, performances of 25 cycle watthour meters 0f the induction type have been found rather undesirable in that the voltage curves takenA thereon did not approach a straight line of constant value, and the load curves for various voltages were relatively different in value. Therefore, when the applied voltage varied from thevoltage for 'which the instrument was calibrated, the

registration at the different loads was incorrect.

I i my invention, I provide means for deiiecting a relatively large part of the flux induced l'by the voltage winding, through the armature when predetermined voltages are impressed thereon, inv order to increase the torque of the armature and overcome the damping effect on the armature at relatively high voltages.

In the accompanying drawings, Figure l is an elevational view of the magnetizable members of a watthour meter embodying my invention; Fig. 2 is a sectional view taken along the line II-II of Fig. 1, and Figs. 3 and 4 are curves showing the results attained with my invention.

Referring to the drawings, my invention ,is used in connection with a laminated'mag- .netizable core member l having a central leg or member 2, two side members 3 which are spaced apart at one end by air gaps 4, and downwardly projecting members 5 spaced from the central member 2 by an air gap 6, A voltage winding (not shown) is ELECTRICAL ll/EASURING INSTRMENT.

lSpecification of Letters Patent.

Patented dan; 7, 1919.

application mea' my 25, una seran no. aflorar.

disposed around the central member 2 and current windings (not shown) are disposed upon the members 5. en armature 6a is disposed in the air gap 6 and it is rotated by a shifting field, asis understood by those versed in the art.

Two magnetizable members 7, severally comprising a body portion 8 and two laterally extended arms 9, are embodied in my invention. The two magnetizable members '7 are attached to opposite sides of the central member by a bolt l0, and the arms 9 extend into the air gaps d, substantially as shown in the drawings. The bolt l() serves the double purpose of maintaining' the` members 7 in position and clamping together the laminations forming the magnetizable core member l. The arms 9 of the members 7 are usually about 1/16 of an inch in length, thereby leaving air gaps 11 between the adjacent ends which prevent.

the members 7 from forming a complete electrical short circuit around the member 2. The shapes of theY performance curves of the meter are influenced by the lengths and sizes of the arms 9, as will hereinafter be described.

rllhe dotted lines l2 that pass through the air gaps t indicate the normal paths of the main magnetic flux induced by the voltage winding. A relatively large part of the flux will tend to crowd through the arms 9,

under normal conditions, since this path is the path of least reluctance.

However, if the load is kcptconstant,

'- when the voltage impressed uponthe voltage winding increases to such value that the arms l) become saturated because of the increase in flux, thereluc'tance of the path l2 through the air gaps L increases and a relatively large part of the flux will traverse a parallel path 13 of relatively less reluctance. Thus, the flux will fringe out into the air gap 6 in greater proportion than the increase in voltage to intercept the armature Ga and thus increase its torque. I If the potential impressed upon the potential winding of an ordinary alternatingcurrent motor-meter increases, the speed decreases because the driving torque increases in accordance with the increase in potential, while the retarding torque that is produced by the potential flux increases in accordance with the square of the increase in potential.

This is seen in the solid line curve in' Fig. 4 which represents the per cent. registration of a wattiiieter at varying voltages and constant load when the members 7 are not used.l

It' the driving torque that is produced by the potential flux is relatively large with respect to the retarding torque produced therey by and can be caused to increase ata greater rate than the increase in potential, as is the case in my device, the increase in the retarding torque may be overcome and a per cent. registration curve, substantially as shown by the broken lines in Fig. 4, may be obtained. Therefore, if the arms 9 are so proportioned that they become saturated above predetermined voltages, relatively more flux will intercept .the armature and the resulting torque, and, consequently, the speed may be caused to be substantially constant -for any value of voltage above the predetermined value. By increasing the length and Width of the arms 9, the value-of voltage at which saturation is reached is increased.

The members 7 are shown as one means for increasing the speed to compensate for the increased retardation at high voltages, but it will be understood that other means may be employed for the same purpose withouty departing from my invention.

Since it has been shown that the voltage curve, at full load, may be made a substantially straight. line of constant Value, it may be shown that, for various loads, the voltage curves may be caused t0 have substantially the saine value. The curves shown in Fig. 3 of the drawings represent the per cent. registration for three different voltages, as 90, 110, and 130 volts, for diierent loads. The difference in .alue of these curves is a very small percentage of their total value and, foi commercial purposes, may be considered to be the saine. Since it was shown, with respect to Fig. 4 of the drawings, tlial, should the device 7 be omitted, the per cent. registration would decrease. as the value of the voltage increases, it may be seen thatthe curves in Fig. 3 would be relatively diti'erent.- in value should the device 7 be omitted.

Although the present construction has been found highly effective and is that which is preferred, it. is obviousI that. modifications may be made within the spirit ot' the invention. and l desire to include all such modifications within the scope of the appended claims.

l claim as my invention:

l. ln an electrical measuring instrument', the, combination with a laminated magnetizable core havinga-central member and side inemebrs spaced from each other atI one end by air gaps` el" two megnetizable niembers resptatively supported by lhe central member at each side lhereoi and having substantially parallel arms disposed in the air gaps.

bers gaps, and means for supporting. thefsaidv l 2.^In an electrical measuring instrument, the combination with a end by air gaps, of two magnetizable memhaving arms extending into the air magnetizable members .at eachside of the laminated magnetizable core having a central member and. side members spaced from each other at one central member of the said magnetizable core. 3. In an electrical measuring instrument,

the combination with a laminated magnet-' y izable core having a. central member and side members spaced from' each other at one end by air gaps, of two inagnetizable members severally comprising a 'bodyportion andv laterally extended arms disposed in the air gaps, and means for attaching said magnetizable members to the magnetizable core member.

4. Iii an electrical measuring instrument, the combination with a laminated magnetizable core having a central member ar side members spaced from eachother at one end by air zgaps, of two magnetizable members severa ly comprising a body portion and laterally extended arms disposed in the air gaps, and means for attaching said magnetizable members to the magnetizable core member and for clamping the laniinations of the saidmagnetizable. core member se, curely together. f

In an electrical measuring instrument, the combination with a magnetizable core having members spaced apart by an air sox.

gap, of two magnetizable members. having laterally extending arms which are disposed in the air gap, and a bolt foi-attaching the said magnetizable members to the said mag netizable core.

6. In an electrical measuring instrument, the combination with a magnetizable core having members spaced apart by a'n air gap,

ot' two magnetizable members severally comportion and laterally ex prising a. body tended arms which are disposed in the air gap.

the combination with a magnetizable core having a central member and side members spaced from each other at one end by air gaps and downwardly projecting members spaced from said central and side members by an air gap, ot' means for deflecting a part ot' the linx which traverses said central and side members to said air gap between said downwardly projectingl members and said central member at predetermined times.

' S. ln an electrical measuring instrument, the combination with a laminated magnet- -izable core havingl a central member and side members spaced t'ronl each other at one end by air gaps. ot' two magnetizable menihers ha ving laterally extending arms that are disposed in the air gaps for increasing 7. In an electrical measuringinstrument,

the reluctance of the path through the air `gaps between the central and side members at predetermined times.

t). In an electrical measuring instrument,

.the combination with a magnetizable core having a central member and side members spaced from each other at one end by air gaps and downwardlyextending members spaced from the cent-ral and side members by an air gap, of means having laterally extending;r arms that are disposed .in the air gaps between for causing the iux that traverses the eentral and side members to be deiiected 'into the air gap between the downwardly extending and the central member under predetermined conditions.

l0. In an electrical measuring" inst-rnthe central and side membersment, the combination with a laminated magnet-Mable core having a central member and side members spaced from each other atl one end by air gaps and integral with each other at their other ends7 of magnetizable means having' laterally extending arms that are disposed in the air gaps between the central and side members Ifor increasing the reluctance, of the air gaps nnder predetermined conditions.

ln testimony whereof, I have hereunto subscribed my namel this 18th day of May, 1911i.

wILLLi-M M. BRADSHAW Witnesses IV. G. MYLIUS, B. B. HINEs. 

